This article reviews current research in the historiography of Great Patriotic War. The authors analyze basic fact of German attack on the Soviet Union trying to answer the question — who was the first to prepare for the war. While some historians appeal to aggressive policies of Germany, many other refer to the international and public policy of the Soviet Union. Lack of documents gives room for a variety of interpretations. Therefore, until nowadays there has been no established opinion on this matter. Among the Russian historians a uniform view on this question is also absent — who is the main instigator of starting the war between the USSR and Germany. Wide spectrum of ideas, absence of sufficient estimations of international activities of Soviet Union on the eve of Great Patriotic war shows that research of this problem has not only historical and cognitive value, but also political implications.Keywords: «Barbarossa» plan, preemptive strike, military and economic potential, a treaty of friendship and cooperation with Yugoslavia.